The invention relates to a shield structure of a rock drilling apparatus for dampening noise, the rock drilling apparatus comprising a feed beam whose one end is a drilling end, whereby the drilling end of the feed beam comprises a first shield part mounted immovably relative to the feed beam, and a second shield part mounted movably relative to the feed beam in its longitudinal direction, whereby both shield parts comprise an opening through which a drill rod, which is connected to a rock drill moving during the drilling on the feed beam, travels during the drilling.
When drilling rock, drill apparatuses are used which comprise one or more booms mounted on a base, and a drill movably mounted on a feed beam provided on the boom. Often the feed beam is also installed at an end of a boom movably in its longitudinal direction by a separate cradle so as to enable the feed beam to be arranged in a desired position and in a desired direction for drilling. In view of these various movements of the boom and the feed beam, the drill apparatus is provided with various transfer cylinders or hydraulic motors known per se that are driven by pressure fluid.
A typical problem in rock drilling is noise. The noise is produced by a rock drill impacting on the head of a tool and the tool impacting on rock, as well as by various other movements, such as rotation, etc. The noise, which propagates even quite widely to the surroundings, keeps causing more and more problems, particularly in the vicinity of housing areas. In order to prevent the noise from causing restrictions on working hours or sites, attempts have been made to solve the issue particularly in surface drilling by using various noise-dampening housings around the feed beam and the drill. Such solutions are known e.g. from WO 2006/038850, WO 00/39412, SE 523874, U.S. Pat. No. 3,667,571, and JP 5-295978. The problem with all these solutions is that they are difficult to implement or they do not dampen the noise over the entire area of the drill. Particularly the noise dampening at the end of the housing, where the drill bit and the drill rod come out of the housing during the drilling, is not good. There have been attempts to solve this problem, for example in WO publication 2006/038851 with a particular dampening solution, which utilizes two damper tubes mounted in the longitudinal direction of the drill rod movably relative to each other. A problem with this solution is that there remains a gap between the parts, and the dampening is not as efficient as it could be.